Like I said :
I converted it as an aiff file with audacity (another lossless format like wav for PCM audio) and mkvtoolnix accepted it (it seems to work).
But I forgot about that part ! (because it really only requires to install audacity - freeware -, to run it, to open the file, and to save it as aiff format)
I can share it but not until tomorrow ('cause via mega it’s going to take time to load it and it’s already getting late where I live).